1. Field of the Invention
The present invention relates to a double-row ball bearing which is particularly adaptable to office automation instruments.
2. Description of the Prior Art
In ball bearings, there is a so-called "direct type of ball bearing" in which a ball race is directly formed in an outer peripheral surface of an axle.
In such a direct type of ball bearing, in case that the ball bearing has a single row of balls only, it is very easy to have the balls aligned with each of an axle ball race (which is formed in an outer peripheral surface of the axle) and an outer-ring ball race (which is formed in an inner peripheral surface of an outer ring). In contrast with this, in case that the ball bearing has a pair of rows of balls, i.e., in case that the ball bearing is of a double-row type, it is very difficult to have the balls and the races aligned with the races.
This will be described with reference to FIG. 10 which shows a conventional double-row ball bearing in which: a pair of axle ball races 101a, 101b are formed in an outer peripheral surface of an axle 100 so as to extend circumferentially; a pair of outer-ring ball races 103a, 103b are formed in an inner surface of an outer ring 102; a plurality of balls 104a and 104b are disposed between the axle ball race 101a and the outer-ring ball race 103a, and between the axle ball race 101b and the outer-ring ball race 103b, respectively.
In the double-row ball bearing having the above construction, the following equation must be satisfied: EQU B&gt;A or A&gt;B
where: "A" denotes the distance between center lines of the axle ball races 101a, 101b; and "B" denotes the distance between center lines of the outer-ring ball races 103a, 103b.
In case that "B" is too much larger than "A" or "A" is too larger than "B", excessive loads are applied to the balls and the races to thereby deform the same so that the ball bearing is damaged.
In the conventional double-row ball bearing, a pair of outer-ring ball races 103a and 103b are previously formed in the inner peripheral surface of the outer ring 102 so as to correspond to the pair of axle ball races 101a and 101b of the axle 1, respectively.
Consequently, such outer-ring ball races 103a, 103b must be formed so as to precisely correspond to the axle ball races 101a, 101b. Further, in assembling of the outer ring 102 with the axle 100, it is necessary to keep the pre-load at a proper value, which requires the assembling work to be conducted in an extremely precise manner. In addition, once the bearing is assembled, the thus assembled bearing can not be adjusted later.